Yes, taping off the grill opening reduces the drag, because, you've eliminated
the drag of the air going over the engine and through that forest of draggy
parts and poor on non-existent exit design for air.
On the Salt flats this was about a 2 mph difference in just reducing the
opening to the front of the car.
Most serious race cars have ducting that takes the airflow from the radiator
and routes it outside or into a low pressure area. The F-1 car are a good
example of how important this radiator flow exit is. They even have the exits
as a winged shape that probably gives a little overall downforce and also
directs the air to the wing. Ferrari is a good example of this.Doing this same
thing on a TR will do the same thing, but don't look for some catastrophic
differences. Maybe at the end of the shute you will be able to pick up another
car or two though. I also taped off the openings between the fenders and the
hood with helicopter tape and this also proved beneficial. On the TR coupe
cutting off the lip of the hard top on the windscreen helped. Air is lazy and
will take the easy way every time.
Ducting air in flexible wire tubing 3" in diameter at 100 miles per hour the
opening is reduced to about 1.5". Smooth tubing retains most of its diameter
as the boundary layer flow increases with the speed. Given that as true, then
it makes sense to make your brake ducting of formed fiber glass over a mold so
the interior is smooth and this allows you to REDUCE the overall diameter (
frontal area) and still have the full benefit. Fun stuff to do and it really
does all count.
Given a good vacant road you can do coast downs without power that will help
to see how the aero dynamics effect the car. When doing these coast down, the
thing is to be very careful to not accidentally cheat.
----- Original Message -----
From: Jack W. Drews
To: fot@autox.team.net
Sent: Saturday, March 05, 2005 9:32 AM
Subject: aerodynamics question
Question for my fellow tech freaks.
I understand that the frontal area that those little air molecules see is
the total profile of the front of the car.
I also understand that the shape of the front changes the wind resistance
(pointed object versus a brick).
my question is this: ignoring the cooling situation, if you replace the
grille in a TR4 with a flat panel, does this change the aerodynamic
resistance?
The NASCAR guys tape off the front opening to go faster...........
uncle jack
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